1. Field of the Invention
The present invention relates to a method of modifying the dye affinity of a cellulose fiber-containing structure and, more particularly, to a method of modifying a cellulose fiber so as to be readily dyed with a dyestuff, particularly such as a disperse dye or an oil soluble dyestuff, which originally possesses less dye affinity for the cellulose fiber.
2. Description of the Prior Art
It is heretofore known that esterification of cellulose fibers can enhance their affinity for a dyestuff such as a disperse dye. The esterification with an acylating agent such as a benzoylating agent, however, impairs the water absorbency of the resulting modified cellulose fiber, a property that is originally present in cellulose fibers.
Further known, for instance, are three methods involving modifying cellulose fibers with a tosylating agent such as p-toluenesulfonyl chloride.
The first method is described in Example 4 in Japanese Laid-Open Patent Application No. 18,778/1975. In this method, a mercerized and bleached cotton fabric was first subjected to pretreatment which involves soaking it in a 50% (w/w) p-toluenesulfonyl chloride solution, squeezing the soaked fabric, allowing it to stand at room temperature for 24 hours, rinsing it with acetone, washing it with water and then drying it. The cotton fabric thus pretreated has a degree of substitution of 0.2 to 0.4. A paper substrate coated entirely with a sublimable disperse dye was then applied to the cotton fabric, and the dye was transferred by pressing at 200.degree. C. for 20 seconds. This method, however, requires a long time for modification and imparts color to the modified cellulose fiber to only a slight extent with the disperse dye.
The second method is described in Example 7 in Great Britain Patent Specification No. 241,854. In this method, one kg. of mercerized cotton was immersed for half an hour in 10 kg. of a 14% alcoholic solution of caustic soda at 20.degree. to 25.degree. C. The fibres were then thoroughly centrifuged, and then immersed in 10 kg. of a 20% solution of para-toluosulphonic chloride in toluol at 40.degree. to 45.degree. C. in which solution they were worked about for an hour. This method, however, presents similar drawbacks as involved in the first method.
The third method is one proposed by the present inventors et al. and disclosed in Great Britain Patent Application Early Publication No. 2,035,386A. This method is a method of dyeing a fiber structure composed of a cellulose fiber or a blend of a cellulose fiber with a synthetic fiber, which comprises the steps of impregnating the fiber structure with an alkaline compound in an amount of from 1 to 20% by weight based on the weight of the fiber structure and with a modifying agent, the molar ratio of the alkaline compound to the modifying agent being from 0.1 to 2.0, and the modifying agent being a compound of the formula: ##STR2## (wherein X is -H, -NO.sub.2, -CH.sub.3 or -SO.sub.2 Cl); effecting the chemical modification of the impregnated fiber structure by heat-treating it under steaming or dry heating conditions; and then dyeing the modified fiber structure with a dye selected from the group consisting of a disperse dye, an oil-soluble dye, a mordant dye, and a basic dye. This method can provide a modified cellulose fiber with a dyeing property while retaining its original water absorbency. This method, however, requires a heat treatment, preferably by steaming, in order to provide a high quality modified fiber, so that additional equipment for steaming is required. As this method also requires the modifying agent to be used in solution in an organic solvent, it requires additional equipment for the organic solvent and the steaming step and an additional step of drying the organic solvent after using the modifying agent prior to the steaming step.
Other methods of chemically modifying cellulose employing p-toluenesulfonyl chloride are reported in, for example, The Journal of the American Chemical Society, vol. 72, pp. 670-674 (1959), Textile Research Journal, vol. 32, pp. 797-804 (1962), Textile Research Journal, vol. 33, pp. 107-117 (1963) and other literature. These methods, however, are industrially inappropriate because they require a long time for modification, or the use of a reagent which is difficult to handle.